Predicting the adsorption capacity and isotherm curvature of organic compounds onto activated carbons in natural waters.

A simple approach to predict the adsorption capacity and isotherm curvature of organic compounds onto activated carbon in natural water was investigated. A combination of the well-known equivalent background compound (EBC), and the simplified competitive adsorption model (SCAM) was employed to delineate the equilibrium capacity. This SCAM-EBC approach may reduce the numerical and experimental effort to obtain the parameters required to predict the adsorption capacity for a specific adsorption system. Several sets of experimental data, including weakly adsorbing (MTBE), strongly adsorbing compounds (TCP, atrazine, and chloroform), and two taste and odor causing compounds (MIB and geosmin) onto different activated carbons in three natural waters and a synthetic groundwater, were tested to verify the SCAM-EBC approach. Based on the approach, a parameter, called relative adsorptivity, describing the adsorption preference of the adsorbent between EBC and the target compound was employed to simulate the isotherm curvature in natural water. The relative adsorptivity of the SCAM-EBC approach is constant and can be directly obtained from the SCAM-EBC parameters in a specific adsorption system. The potential and extent of isotherm curvature can be simulated by only changing the parameter of relative adsorptivity. The marked isotherm curvature was found while the relative adsorptivity is larger than 2.0 to 4.0 for all the systems tested.

Competitive and hindering effects of natural organic matter on the adsorption of MTBE onto activated carbons and zeolites.

Equilibrium and kinetic adsorption of methyl tert-butyl ether (MTBE) onto three coal-based activated carbons, one coconut-based activated carbon, and two zeolites are elucidated in this study. Natural organic matter (NOM) and MTBE competed for the adsorption of activated carbons to different extents. The ideal adsorbed solution theory (IAST) combined with the equivalent background compound (EBC) model can adequately describe the NOM competition and predict the isotherms of MTBE onto the activated carbons. No competitive adsorption was observed for one of the zeolites, mordenite, due to the molecular effect. Besides, the aperture size, and the SiO2/Al2O3 ratio of the zeolite may also play an important role in the adsorption of MTBE from the aqueous phase. The surface diffusion model accurately simulated the transport of MTBE within the adsorbents employed in different water matrices. For all the activated carbons tested, the surface diffusivity of MTBE in natural water was nearly equal to that in deionized water, indicating that no apparently hindering effect occurs. A much slower adsorption kinetic of mordenite in natural water was observed since the opening apertures on mordenite may be appreciably hindered and blocked by NOM.

The small subunit ribosomal RNA gene sequence of Pleistophora anguillarum and the use of PCR primers for diagnostic detection of the parasite.

Using the polymerase chain reaction (PCR) and two primers for conserved regions of the small subunit ribosomal RNA (SSU-rRNA) of Microsporidia, a DNA segment about 1,195 base pairs long was amplified from a DNA template prepared from purified spores of the microsporidian species Pleistophora anguillarum. These spores had been isolated from adult eels (Anguilla japonica) with "Beko Disease." A comparison of sequence data from other microsporidian species showed P. anguillarum SSU-rRNA to be most similar to Vavraia oncoperae. When juvenile eels were artificially infected with P. anguillarum, enzyme-linked immunosorbent assay could detect a positive infection only 12 days post-infection. However, when suitable PCR primers were used, a DNA fragment of about 0.8 kb was detected from these juvenile eels after only 3 days post infection. No PCR product was obtained with templates prepared from clinically healthy control animals.

Helicobacter pylori-seronegative gastric carcinoma: a subset of gastric carcinoma with distinct clinicopathologic features.

BACKGROUND/AIMS: The frequent association of gastric atrophy and intestinal metaplasia in gastric cancer (GC) might preclude serologic detection of Helicobacter pylori (H. pylori) infection in GC. By using polymerase chain reaction (PCR) for detection, we would like to determine whether there exists a subset of genuinely H. pylori-negative GC patients, and whether they have distinct clinicopathologic features or not. METHODOLOGY: IgG antibodies against H. pylori were determined by ELISA in sera, and H. pylori DNA was detected by PCR in resected gastric specimens from 160 GC patients. Clinicopathologic characteristics were then compared among group A: seropositive, group B: seronegative but PCR-positive, and group C: seronegative and PCR-negative. RESULTS: Among 160 patients, 105 (65.6%) were classified as group A, 25 (15.6%) as group B, and 30 (18.8%) as group C. Group B patients were older and had more infiltrative tumor growth than group A. Group C had a significantly higher frequency of female predominance, and their cancers were of a more cardiac location and of the diffuse histologic subtype than those of groups A and B. CONCLUSIONS: A significant portion (15.6%) was negative to ELISA but positive to PCR, suggesting that older ages and infiltrative tumor growth might preclude serologic detection of H. pylori infection by impairing humoral responses. Although the majority (81.2%) has a strong association with H. pylori infection, an H. pylori-negative subset indeed exists and has distinct clinicopathologic features, supporting that causes other than H. pylori infection are involved in GC carcinogenesis.

Immunoglobulin A nephropathy and ankylosing spondylitis. Report of two patients in Taiwan and review of the literature.

We describe 2 patients with immunoglobulin A (IgA) nephropathy in association with ankylosing spondylitis. Renal biopsy demonstrated mesangial proliferative glomerulonephritis with prominent IgA, C3c, and less intense properdin deposition in the glomeruli. Intraglomerular clumps of virus-like particles were also observed in the kidney sample from one patient (case 2), who had an abnormal liver function. Our findings support the hypothesis that here is a possible common pathogenesis responsible for the concurrence of both IgA nephropathy and ankylosing spondylitis.